Design Of Centralized Protection For Smart Traction Substation

The high-speed railway mileage of our country has reached11028km, which makes our country’s operating mileage of high-speed railway longer than any other country in the world. Traction substation provides power for high-speed railway, with the publishing of IEC61850and the rapid development of communication and computer technology, significant changes have taken place in traction substation automation system. At the same time, the digital traction substation has been put into operation, smart traction substation will be the development direction of traction substation technology.Based on the differential functions, the existing protective configuration of traction substation is arranged by the "one on one" way. Therefore the feeder protection and transformer protection are independently configured. This configuration has some defects, for example, when it needs other interval protections as a backup and to guarantee the selectivity, the backup protection will set a longer time limit so that it cannot quickly solve the fault; when the circuit breaker failure occurred, generally the upstream breaker needs to open in order to remove the faults, but this way expands the scope of power failure; for some special circumstances, the maloperations of feeder protection cannot be judged correctly.Centralized protection, which is achieved by a server on dealing with the existing disadvantages in the protection configuration, is put forward in this paper. Centralized protection not only has traditional functions, but also has two extra functions which are cooperative backup protection and area backup protection. Moreover, the principle, action logic and flow chart of the cooperative backup protection and area backup protection are given. After the completion of the function design, the communication network scheme of traction substation with centralized protection has been given. Under Windows platform, program task modules is divided through multi-threading and thread synchronization technology, and kernel event object is built up corresponding to thread function. In the program design of the centralized protection function:data reception task module program is implemented with the network interface of WinPcap which can receive and analysis the IEC61850-9-2and GOOSE. Protection task module program is implemented for the calculation of electrical data and logic judgment of movement. Communication task module program is implemented for sending GOOSE messages and the GOOSE messages contain the conditions of circuit breaker and disconnector.Finally, the test platform has been built by PNF803digital relay protection tester, PCS-222B intelligent operation box, mimic disconnecting switch, photoelectric converter and a server. The feeder line protection and cooperative backup protection of centralized protection have been tested to prove that protection software task partitioning is reasonable, data reception and analysis are accurate, function and logic is correct, GOOSE message is reliable and mimic disconnecting switch can operate accurately.